The present invention relates to an electrode for electrolyzers, the electrode being of the type which comprises several parts which are mutually joined by means of a mechanical joint. Multiple-part electrodes of this type are often used, e.g. to arrange electrical connections, to join load bearing parts with chemically active parts and particularly to design bipolar electrodes in which the electrode acts as an anode on one side and as a cathode on the other and where there, as a rule, are different requirements on the materials. It is well known that the selection of joint type often gives rise to serious problems in connection with electrodes since several conditions which are special for this use must be fulfilled besides those which are normally considered for mechanical joints, such as strength and a simple and economical design. For electrode joints the usually very corrosive environment in which the electrode is intended to work must be considered and this places special demands on choice of material and a constructive design. The contact surface between different materials must be kept free from electrolyte but can nevertheless change with time due to proton migration through certain metals. On the other hand, if there are cavities in the construction there is a risk that hydrogen gas of a very high pressure will accumulate in these. Space is often limited which means that sophisticated joints cannot be used. Further, the joint must be such that the dimensions of the electrode will be maintained during a long time also at fairly large temperature variations as electrolyzers are often operated at elevated temperatures. Dimension changes can cause a changed distance and thus a changed resistance between the electrochemically active surfaces resulting in a decreased efficiency or in leaks leading to current or electrolyte leakage. Last but not least, the joint must fulfil high demands on electric conductivity as high currents and current densities are usually used. A particular problem in connection with this is that the contact surface tends to change with time and to age, resulting in an increased electrical resistance. The problems are especially pronounced when chemically unstable materials are used in the electrode.
Several types of joints have been used in connection with electrodes. Bolting is a common method which allows high flexibility in the design. However, the contact pressure will not be uniform and will be high only near each bolt. Further, the joints have several cavities and the final constructions tend to be ungainly and heavy. The possibilities to use welding are limited since several electrode materials cannot be welded to each other and welding can further lead to built in stresses in the construction which will appear at ageing and temperature variations. Further, welded joints cannot be released and they often leave cavities in the joint. Explosion welding gives a good electrical conductivity but is a costly method which further can lead to a tendency to bending at thermal expansion, an erratic stability of the joint and less reproducible results. With press- and shrinkage-joints sufficiently high contact pressures can be maintained so that a hydride formation due to proton migration will not occur. However, the joints will easily become complicated with a risk of dimension changes at subsequent welding.